Most of the exercises would be perfect for muscle building, more so for those that had not done weights before, since most of them, once you look at them, are only weightless versions of a squat, Bulgarian/split squat, a bench press upside down (press-up), incline/decline press-ups, then the triceps work against the bench is similar in movement to the triceps extension but with bodyweight.

So, yes, it can and does work, it's ideal if people can't get to a gym or just want to maintain basic strength and not progress to massive loads, for the latter a gym and/or weights would be required. That said, I have seen a guy that increased his one arm jerk with handstand push-ups etc and never touched a weight for a number of weeks but still managed to set a PR when he did the jerk.

If you know what you're using them for and how to effectively use them, they work, but they will have their limits as well.